1. Field of the Invention
The present invention relates to a method for immobilizing a biomolecule on a solid substrate, and more particularly, to a method for noncovalently immobilizing a biomolecule on a solid substrate.
2. Description of the Related Art
The term “microarray” refers to a substrate in which specific molecules are densely immobilized in a predetermined region. Examples of the microarray include, for example, a polynucleotide microarray and a protein microarray. The term “polynucleotide microarray” refers to a substrate on which polynucleotides are densely immobilized in each predetermined region. The microarray is well known in the art, for example, U.S. Pat. Nos. 5,445,934 and 5,744,305.
A polynucleotide is immobilized on a solid substrate by synthesizing a polynucleotide directly on a substrate or by immobilizing a polynucleotide previously synthesized at a predetermined location on a substrate (spotting method). Polynucleotide microarrays and methods of producing the same are described in U.S. Pat. Nos. 5,744,305, 5,143,854 and 5,424,186, the disclosures of which are incorporated herein in their entirety by reference. The spotting method is widely used to covalently immobilize a biomolecule on a solid substrate. For example, a biomolecule is generally immobilized on a solid substrate by activating a surface of the substrate with a nucleophilic functional group, such as an amino group, to which a biomolecule, for example, a polynucleotide, activated with a good leaving group is coupled, and then removing unreacted reactants from the substrate. A method for noncovalently immobilizing a biomolecule on a substrate has not been known in the art.
Polyethylene glycol, a hydrophilic compound, has been used in a microarray. Polyethylene glycol was attached to both ends of a DNA strand via a covalent bond and the DNA strand was immobilized on a substrate to obtain a microarray [Journal of Experimental hematology 2003: 11(4): 393-397]. US-2003-0108917-A1 describes a method of producing a microarray by immobilizing a probe polynucleotide on a hydrogel comprised of a star-like polyethylene glycol derivative having an epoxy group at its terminal.
However, in these methods, the biomolecule is covalently immobilized on the substrate. That is, the substrate or the biomolecule should have a reactive functional group attached thereto. In addition, a covalent bond may be formed in severe reaction conditions. Further, it is difficult to control the reaction conditions and the operation is complicated. Furthermore, unreacted reactive substances must be removed after the completion of the reaction.
The present inventors conducted research and discovered a method for noncovalently immobilizing a biomolecule on a solid substrate, the method providing a microarray having a strong quality to be efficiently used in an analysis of a target molecule.